Cell Division and Protein Synthesis Flashcards

Comprehensive vocabulary flashcards covering the cell cycle, DNA replication, stages of mitosis, gene expression, transcription, translation, cell growth regulation, and aging.

Cell Cycle

A series of changes a cell undergoes from the time it is formed until it reproduces, consisting of Interphase and M (mitotic) phase.

Interphase

The period from cell formation to cell division during which the cell carries out routine activities, maintains nuclear material in an uncondensed chromatin state, and prepares for division through $G_1$, S, and $G_2$ subphases.

$G_0$ Phase

The state entered by cells that permanently cease dividing and are no longer actively in the cell cycle.

S Phase

The synthetic subphase of interphase in which nuclear DNA replication occurs prior to cell division.

Replication Fork

The specific point where double-stranded DNA unwind and unzip to separate two template strands during DNA replication.

DNA Polymerase

The enzyme that attaches to an RNA primer and adds complementary nucleotides to synthesize new DNA strands during replication.

DNA Ligase

The enzyme that splices short, discontinuous segments of the lagging strand together during DNA replication.

Semiconservative Replication

The process of DNA replication in which each newly formed double-stranded DNA molecule is composed of one old template strand and one newly synthesized strand.

Mitosis

The nuclear division phase of mitotic cell division, consisting of prophase, metaphase, anaphase, and telophase.

Prophase

The first phase of mitosis during which chromatin condenses into chromosomes, centrosomes move toward opposite poles to form the mitotic spindle, and the nuclear envelope breaks down.

Kinetochore

A specific area on chromosome centromeres where special microtubules attach during late prophase to align chromosomes at the cell equator.

Metaphase

The stage of mitosis where the centromeres of chromosomes are precisely aligned along the metaphase plate midway between the poles.

Anaphase

The shortest phase of mitosis during which sister chromatid centromeres split simultaneously and motor proteins pull individual chromosomes toward opposite poles.

Telophase

The final stage of mitosis that begins when chromosome movement stops, leading to nuclear membrane formation, nucleoli reappearance, and uncoiling of chromosomes into chromatin.

Cytokinesis

The division of the cell cytoplasm starting in late anaphase, where a ring of actin microfilaments contracts to form a cleavage furrow that pinches two daughter cells apart.

Contact Inhibition

A cellular stop signal that causes normal cells to stop dividing when they come into contact with other cells.

Cyclins

Regulatory proteins that accumulate during interphase and activate cyclin-dependent kinases (CDKs) to propel the cell through cycle checkpoints before being destroyed.

$G_1$ Checkpoint (Restriction Point)

The primary and most critical cell cycle checkpoint; if a cell fails to pass it, it enters the non-dividing $G_0$ phase.

Gene

A segment of DNA that holds the genetic code for the synthesis of one polypeptide.

Triplet Code

A specific sequence of three consecutive nitrogen bases in DNA that codes for a particular amino acid.

Exons

The coding segments of a gene that remain in mature mRNA and express amino acid sequences.

Introns

Noncoding segments of DNA interspersed amongst exons that are removed during pre-mRNA processing.

Transcription

The process of transferring genetic code held in DNA base sequences into complementary base sequences of messenger RNA.

Promoter

A special DNA sequence located at the starting point of a gene that binds transcription factors and RNA polymerase on the template strand.

RNA Polymerase

The enzyme that unzips DNA and aligns complementary RNA nucleotides matching the DNA template strand to synthesize mRNA.

Spliceosomes

Special protein complexes that remove noncoding introns from pre-mRNA and splice together coding exon regions.

Codon

A three-base sequence on mRNA that corresponds to a specific DNA triplet code and specifies an amino acid or stop signal.

Transfer RNA (tRNA)

Carrier RNA molecules that possess an anticodon at one end and transport a specific amino acid to the ribosome during translation.

Anticodon

A specific triplet code on tRNA that complementary base-pairs with a codon on mRNA at the ribosome.

Translation

The process of decoding mRNA base sequences at ribosomes with tRNA assistance to assemble polypeptide chains.

Polyribosome

A complex consisting of a single strand of mRNA bound to multiple ribosomes translating it simultaneously to generate numerous copies of a protein.

Autophagy

The process of self-digestion where a cell sweeps up damaged organelles and cytoplasmic debris in autophagosomes for degradation by lysosomes.

Ubiquitin

A specialized protein tag attached to unneeded, misfolded, or damaged cellular proteins to designate them for degradation.

Proteasomes

Protein complexes that recognize and disassemble ubiquitin-tagged proteins into reusable amino acids.

Apoptosis

Programmed cell death mediated by mitochondrial chemical leakage and caspase enzyme activation, leading to DNA degradation and phagocytosis.

Cell Differentiation

The development of specific structural features and specialized functions in cells as specific genes are turned on or off.

Hyperplasia

Accelerated cell division that increases cell numbers in response to elevated physiological demand.

Atrophy

A decrease in organ or tissue size resulting from the loss of hormonal stimulation or disuse.

Telomeres

Protective nucleotide structures capping chromosome ends that shorten after every round of cell division.

Telomerase

An enzyme present in embryonic germ cells and cancer cells that lengthens telomeres, granting unlimited cell division potential.

Progeria

A rare genetic disease caused by defective progerin in the nuclear lamina, resulting in nuclear instability and accelerated physical aging.